The disgruntled ex-chief of telecom firm Inter-Tel has made what looks like a lowball offer to take his company private, offering roughly $600 million.

Steven Mihaylo, who founded Inter-Tel in 1969 and still owns 20 percent of the company, submitted a takeover offer yesterday at $22.50 a share – a 12 percent premium to Wednesday’s closing price.

Mihaylo is working with San Francisco-based private equity firm Vector Capital.

The Post reported in April that Mihaylo and Vector were gearing up to make a takeover offer.

Several Inter-Tel shareholders said yesterday the offer was too low and probably won’t be accepted by the board. It’s unclear whether Mihaylo would raise his offer if it is rejected or if the company will be forced to put itself on the block.